SPN Fault Codes Verified Factory Specs

SPN 107 FMI 3: Engine Air Filter Restriction High Voltage Protocol

Diagnostic trouble guide for SPN 107 FMI 3 (Engine Air Filter Differential Pressure Circuit Voltage High / Open Circuit). Filter Minder vacuum checks and sensor wiring.

SPN 107 FMI 3 Low (Maintenance Warning)

System Overview: Air Induction System

Air filter restriction sensor signal voltage exceeded 4.85 Volts DC, indicating an open circuit in the sensor return line.

Driver Symptoms

Yellow air cleaner restriction indicator warning on dash display
Normal engine power maintained (no derate unless intake restriction exceeds 25 in-H2O vacuum)

Probable Causes

Disconnected harness connector at the air intake duct restriction switch
Broken sensor ground wire in engine front harness
Completely plugged primary air filter element

Diagnostic Steps

Inspect visual mechanical restriction sight glass gauge (Filter Minder) on air box ducting
Check 5V reference supply and ground across the 2-pin connector
Replace primary and secondary safety air filter elements if restriction exceeds 20 in-H2O (5.0 kPa)

Sensor Wiring Pinout: 2-Pin Connector: Pin 1 (+5V / Signal), Pin 2 (Chassis Ground Return)